Personal health benefits of not driving.

I've been hypothesizing for some years that if only Americans walked, cycled, and rode public transportation (thus needing to walk or run to make a train/bus/tram/etc.), that obesity levels would be decreased. (I also think that if companies didn't sell sizes in 3XL or greater, people would have less incentive to allow themselves to become obese - but this is a less tenable hypothesis, I think.)

Well, No Impact Man has posted a graph showing relationships between people in different countries. I would argue that he shouldn't have used a line graph, since a line graph shows an implicit relationship between values on the x-axis. Categorical data - such as countries - should be shown as columns or bars. However, the apparent inverse relationship between obesity (red) and daily physical transportation activity (green). Of course, there are several possible variables that are affecting these results, including diet, portion size, affluence, and stress to name a few.

Results like this, however, seem interesting to me. However, I would like to know if something like this relationship could be replicated within a country, or even within a major city served by public transportation (such as NYC). Would you be able to find a similarly inverse relationship based on borough, distance-to-work, or diet? Similarly, would there be a difference between people who ride public transportation vs cycle? (I'm assuming that there is - but this raises the additional question of whether cyclists are a self-selecting group...)

Ahh... the internal mental debate continues.

Of course, you could probably show a relationship between %urbanized and obesity. (I'm hypothesizing that more rural communities are more obese than highly urban communities.) Anyone with data?